Digital logic circuits and components: logic gates, Boolean algebra, map simplifications, combinational and sequential circuits, flip-flops, registers and counters, memory unit. - Question Bank

1. What is the minimum number of NAND gates required to implement an AND gate?
A) 1
B) 2
C) 3
D) 4
2. Which memory type is generally faster and more expensive per bit than DRAM?
A) SRAM
B) DRAM
C) ROM
D) EEPROM
3. Which memory type uses transistors and capacitors to store data?
A) SRAM
B) DRAM
C) ROM
D) Flash Memory
4. What is the purpose of a 'preset' or 'clear' input on a flip-flop?
A) To synchronize with the clock
B) To asynchronously set or reset the flip-flop's state
C) To control the data input
D) To enable the output
5. Which of the following is a characteristic of a synchronous sequential circuit?
A) Asynchronous transitions between states
B) Propagation delays affecting state changes
C) All flip-flops triggered by a common clock
D) Outputs depend only on current inputs
6. What is a 'state' in the context of sequential circuits?
A) The current input value
B) The output of the combinational logic
C) The current values stored in the flip-flops
D) The clock signal frequency
7. A T flip-flop toggles its output when the T input is:
A) 0
B) 1
C) High
D) Low
8. Which type of flip-flop avoids the indeterminate state of an SR flip-flop by having J and K inputs connected together?
A) D flip-flop
B) T flip-flop
C) JK flip-flop
D) SR flip-flop
9. An SR latch with S=1 and R=1 results in an invalid or indeterminate state for:
A) SR latch
B) JK latch
C) D latch
D) T latch
10. What is the primary function of a clock signal in sequential circuits?
A) To provide data input
B) To synchronize state changes
C) To perform arithmetic operations
D) To reset the circuit
11. A full-adder circuit adds three bits (two input bits and a carry-in) and produces a sum and a:
A) Carry-out
B) Carry-in
C) Overflow
D) Parity bit
12. A half-adder circuit adds two bits and produces a sum and a:
A) Carry-out
B) Carry-in
C) Overflow
D) Parity bit
13. Which Boolean algebra property states that A . (B + C) = (A . B) + (A . C)?
A) Commutative Property
B) Associative Property
C) Distributive Property
D) Absorption Property
14. Which Boolean algebra property states that A + (B + C) = (A + B) + C?
A) Commutative Property
B) Associative Property
C) Distributive Property
D) Identity Property
15. The expression A . 1 is equivalent to:
A) 0
B) 1
C) A
D) A'
16. The expression A + 0 is equivalent to:
A) 0
B) 1
C) A
D) A'
17. Which logic gate outputs 0 if either input is 0, and 1 only if both inputs are 1?
A) OR gate
B) AND gate
C) NOT gate
D) NAND gate
18. A demultiplexer (DEMUX) performs the reverse operation of a multiplexer. It takes a single input and routes it to one of several output lines, controlled by:
A) Data inputs
B) Clock signals
C) Select lines
D) Enable signals
19. A multiplexer (MUX) is a combinational circuit that selects one of several input lines and routes it to a single output line. The selection is controlled by:
A) Data inputs
B) Clock signals
C) Select lines
D) Reset lines
20. An encoder circuit performs the reverse function of a decoder. It takes multiple inputs and produces a binary code representing the active input. It is a type of:
A) Sequential circuit
B) Combinational circuit
C) Flip-flop
D) Memory unit
21. A decoder circuit takes a binary input and activates one of its multiple output lines based on the input value. It is a type of:
A) Sequential circuit
B) Combinational circuit
C) Register
D) Counter
22. Which type of RAM requires periodic refreshing to maintain its data?
A) SRAM
B) DRAM
C) ROM
D) EEPROM
23. Which of the following is a type of RAM that uses latches to store each bit?
A) DRAM
B) SRAM
C) ROM
D) PROM
24. What does ROM stand for?
A) Random Access Memory
B) Read Only Memory
C) Register Only Memory
D) Read Arithmetic Memory
25. What does RAM stand for?
A) Read Access Memory
B) Random Access Memory
C) Register Access Memory
D) Read Arithmetic Memory
26. Which type of memory is non-volatile and retains its data even when power is off?
A) SRAM (Static RAM)
B) DRAM (Dynamic RAM)
C) ROM (Read-Only Memory)
D) Cache Memory
27. Which type of memory is volatile and loses its data when power is turned off?
A) ROM (Read-Only Memory)
B) RAM (Random Access Memory)
C) Flash Memory
D) EEPROM (Electrically Erasable Programmable Read-Only Memory)
28. A BCD counter counts from:
A) 0 to 7
B) 0 to 9
C) 0 to 15
D) 0 to 16
29. What is the maximum number of states a 3-bit counter can represent?
A) 3
B) 6
C) 8
D) 16
30. A synchronous counter has:
A) A ripple effect in state transitions
B) All flip-flops triggered by the same clock pulse
C) Independent clock signals for each flip-flop
D) Slower state transitions
31. What is a ripple counter?
A) A synchronous counter where all flip-flops change state simultaneously
B) An asynchronous counter where the output of one flip-flop clocks the next
C) A counter that counts up and down
D) A counter that counts in BCD format
32. A counter is a sequential circuit that goes through a predetermined sequence of states upon the application of:
A) Data inputs
B) Control signals
C) Clock pulses
D) Reset signals
33. A shift register can be used to:
A) Convert serial data to parallel data
B) Convert parallel data to serial data
C) Both (a) and (b)
D) Perform logical AND operations
34. What is the main function of a register?
A) To perform arithmetic operations
B) To store a group of bits
C) To control the timing of operations
D) To convert analog signals to digital
35. A D flip-flop is also known as a:
A) Toggle flip-flop
B) Delay flip-flop
C) Set-Reset flip-flop
D) Master-slave flip-flop
36. What is the characteristic equation for a JK flip-flop?
A) Q(t+1) = JQ' + J'Q
B) Q(t+1) = D
C) Q(t+1) = KQ' + K'Q
D) Q(t+1) = Q XOR K
37. Which type of flip-flop is sensitive to the rising edge of the clock pulse?
A) Level-triggered SR flip-flop
B) Edge-triggered D flip-flop
C) Level-triggered JK flip-flop
D) Asynchronous T flip-flop
38. A flip-flop is a type of:
A) Combinational circuit
B) Sequential circuit
C) Logic gate
D) Memory unit
39. Which of the following is an example of a sequential circuit?
A) Decoder
B) Multiplexer
C) Flip-flop
D) Encoder
40. A sequential circuit's output depends on its:
A) Current input only
B) Current input and current state
C) Current state only
D) Previous input only
41. Which of the following is an example of a combinational circuit?
A) Shift register
B) Counter
C) Adder
D) RAM
42. A combinational circuit's output depends only on its:
A) Current input
B) Previous output
C) Current state and previous input
D) Past inputs
43. What does the Karnaugh map (K-map) method simplify?
A) Sequential circuits
B) Combinational circuits
C) Memory units
D) Flip-flops
44. In Boolean algebra, the expression A + A' is equal to:
A) 0
B) 1
C) A
D) A'
45. De Morgan's theorem states that (A + B)' is equivalent to:
A) A' + B'
B) A' . B'
C) A . B
D) A + B
46. What is the Boolean expression for the NAND gate with inputs A and B?
A) (A + B)'
B) (A . B)'
C) A' + B'
D) A' . B'
47. Which gate is considered a universal gate, meaning any other logic gate can be constructed using only this type?
A) AND gate
B) OR gate
C) NAND gate
D) XOR gate
48. The NOT gate is also known as an inverter because it:
A) Outputs the same as the input
B) Outputs the complement of the input
C) Outputs 1 if any input is 1
D) Outputs 0 if any input is 0
49. What is the Boolean expression for an OR gate with inputs A and B?
A) A + B
B) A . B
C) A'
D) A XOR B
50. Which logic gate produces an output of 1 only if all of its inputs are 1?
A) OR gate
B) AND gate
C) NOT gate
D) XOR gate
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